[php-src] Issue #22115: Tracing JIT: side-exit SNAPSHOT omits a loop-PHI register, interpreter resumes

Issue: https://github.com/php/php-src/issues/22115 Author: wilaak ### Description ### Description tracing jit gives wrong answer on a hot loop. function jit and jit=off are fine so it's a tracing thing. The following code: ```php <?php declare(strict_types=1); function lookup(string $tape, array $meta, array $state_meta, string $path): int { $length = \strlen($path); $state_offset = 0; $cursor = 1; while ($cursor < $length) { $run = \strcspn($tape, $path[$cursor], $state_offset, 1); if ($run < 1) { $m = (int) $meta[$state_offset]; $edge_length = $m & 0xFF; if ($edge_length === 1 || \substr_compare($path, "c", $cursor + 1, 1) === 0) { $cursor += $edge_length; $state_offset = ($m >> 32) & 0xFFFFFF; continue; } } return (int) $state_meta[$state_offset]; } return (int) $state_meta[$state_offset]; } $tape = "ab"; $meta = [0 => 1 | (1 << 32), 1 => 2 | (2 << 32)]; $state_meta = [0 => 100, 1 => 200, 2 => 300]; for ($w = 0; $w < 2000; $w++) { lookup($tape, $meta, $state_meta, '/abc'); lookup($tape, $meta, $state_meta, '/abx'); } var_dump(lookup($tape, $meta, $state_meta, '/abx')); ``` Resulted in this output: ``` $ php -d opcache.enable_cli=1 -d opcache.jit_buffer_size=64M -d opcache.jit=tracing repro.php int(100) ``` But I expected this output instead: ``` $ php -d opcache.enable_cli=1 -d opcache.jit_buffer_size=64M -d opcache.jit=function repro.php int(200) ``` ### Probable cause the IR: ``` php -d opcache.enable_cli=1 -d opcache.jit=tracing \ -d opcache.jit_buffer_size=64M \ -d opcache.jit_debug=$((0xFFFFFFFF)) repro.php 2>&1 | less ``` exit_8 is the bad one, CV5($state_offset):int with no (r12). ### Environment php 8.5.6 cli, opcache 8.5.6, linux wsl2, gcc 14. master at fcc29c8d. ### PHP Version ```plain PHP 8.5.6 (cli) (built: May 14 2026 16:01:51) (NTS) Copyright (c) The PHP Group Built by Ubuntu Zend Engine v4.5.6, Copyright (c) Zend Technologies with Zend OPcache v8.5.6, Copyright (c), by Zend Technologies ``` ### Operating System Ubuntu 24.04.1 LTS (Noble Numbat) on WSL2, kernel 6.6.